The biggest question at the Olympics has not been how many swimming medals the United States has won, but what the heck are those giant purplish dots on the back of Olympic swimming champ Michael Phelps?

The games in Rio brought new focus to cupping, one of the oldest methods used in traditional Chinese medicine. It dates to the early fourth century, when “fire jar qi” was described by herbalists as a remedy for alleviating headaches, dizziness and abdominal pain.

Original practitioners used hollowed-out animal horns for cups that were placed over particular acupuncture points, using the heat of fire to create suction on the skin and underlying tissues. The tension-and-release action of suction is believed to loosen tight muscles.

It also causes capillaries just beneath the surface of the skin to rupture, creating circular bruises that range in color from a healthy pale pink that disappears in a few hours, to the deep purple seen on Phelps. They can last for a few days, which practitioners say is a sign of stagnant blood. The vacuum formed by cupping draws up noncirculating, stagnant blood to the skin’s surface to restore circulation to the affected areas below.

Today cupping is still used by acupuncturists as an adjunct treatment with acupuncture for longer-lasting results.

In interviews, Phelps said he asked for the treatment due to soreness in his right arm.

“Pain is usually the result of poor circulation. I wouldn’t be surprised if he’s also doing acupuncture,” said Christina Kapothanasis, a licensed acupuncturist and specialist in Oriental medicine at Kai Traditional Chinese Medicine and Acupuncture Clinic in Kakaako, where plastic cups are used with a device that sucks oxygen out of the cup once it is placed on the skin. “It’s unusual for people to ask for cupping alone because they work together.”

Acupuncture needles open the tissues to let blood flow in and also release endorphins that reduce the hormone cortisol, she said. Cortisol prevents the release of substances that cause inflammation in the body, but high cortisol levels weaken the immune system and are associated with destroying healthy muscle and bone, slowing healing and cell regeneration, impairing digestion, metabolism and mental function, and interfering with healthy endocrine function.

The effects of cupping are similar to acupuncture, Kapothanasis said.

The Kai clinic charges $95 for an initial combination treatment of acupuncture and cupping $75 after that.Studies of people with neck pain and arthritic pain have shown reduced pain after three to four months of cupping treatment, but scientists do not discount the placebo effect because blind testing is difficult when it involves attaching cups to parts of the body.

“It doesn’t hurt at all,” said Lynn Wong, who was being treated at the clinic for back and shoulder pain. “It’s really relaxing. I would come here every day if I could.”

At Laka Skin Care & Spa, traditional fire cupping with glass cups is a $25 add-on service for any massage treatment. Owner Akiko Chun began offering the service two years ago, demystifying the process by introducing it via a series of workshops. She said it doesn’t hurt, and the therapist glides the cup across the back and legs during the massage “so it feels like a four-handed massage.”

In the athletic department at the University of Hawaii at Manoa, head trainer Eric Okasaki is amused by the surge in interest in cupping. “It’s nothing new,” he said. “It’s a recognized form of treatment, just another way to increase circulation.”

For student athletes, Okasaki said, “We do whatever certified athletic trainers are trained to do.” Their basic “bag of tricks” for dealing with muscle pain includes rest, ice compression and elevating the affected area. Acute new injuries might call for heat and other practices that increase blood circulation.

Cupping is just one of many treatments the trainers need to be familiar with, Okasaki said.

“We have to be aware of what is happening nationwide and worldwide because we have such a diverse ethnic population and a foreign population of athletes,” he said. “They may have certain needs, and we have to be aware of them, just like in Hawaii we know certain things work that are not recognized by Western medicine.

“We rely on medical people in the community for help. It’s a small community, and many of them are fans of UH and want to help. If it involves cupping, fine. If it involves acupuncture or chiropractics, fine.”

Chris Ranes, owner of Fitness Ranes, agreed that cupping is one of many therapies that might help athletic performance and recovery, which starts with the body’s nervous system. It’s the nervous system that controls movement and hand-eye coordination needed for athleticism.

“The sympathetic nervous system stimulates the body’s fight-or-flight response. Athletes pretty much live in that kind of state,” he said. “The parasympathetic nervous system has more to do with rest and recovery, what you do when you sleep, with what you do with your time off. Massage, ice packs, stretching, breathing and exercise all help recovery in some way.”

For overall health, the sympathetic and parasympathetic systems should be in balance. He said he often works with stressed executives whom he has to treat like over-trained athletes.

“People who are stressed out usually have tense necks and muscles,” Ranes said. “Even without going through athletic training, I find them to be in an over-trained, fight-or-flight state.”

Which means there are a lot of nonathletes who can also benefit from recovery methods used by elite athletes.

Okasaki said, “Whoever’s offering cupping treatments now, they’re going to make a lot of money because people want to try it.”